The overall objective of this work is to explore the use of hormonally active compounds for reducing the abundance or vectorial capacity of mosquitoes. We shall determine whether juvenile hormone is present in diapausing as well as non-diapausing adult Culex pipiens mosquitoes. Since ovarian diapause is reportedly due to a temporary absence of this hormone, we will attempt to identify the factors that initiate and terminate diapause. We will determine whether juvenile hormone controls the maturation of the midgut epithelium. The development of intracellular organelles as well as the peritrophic membrane will be correlated with the hormonal milieu of adult A. aegypti mosquitoes. We shall study the course of infection of sigma virus in A. aegypti and C. pipiens mosquitoes. Multiplication of virus will be studied as well as the response of infected insects to CO2. We shall determine optimum conditions for invasion of this agent into the ovaries. BIBLIOGRAPHIC REFERENCES: Troy, S., Anderson, W.A., and Spielman, A. Lipid content of maturing ovaries of Aedes aegypti mosquitoes. Comp. Biochem. Physiol., 50B:457-461, 1975. Spielman, A. Inherited infection in the epidemiology of diptera-borne disease: perspectives and an introduction. Ann. N.Y. Acad. Sci., 266:115-124, 1975.